Pneumatic rubber tires are produced by molding and curing a green tire in a tire press. The green tire is pressed outwardly against a mold surface by an inner bladder which is expanded inside the tire by fluid. The green tire is shaped against the mold wherein the sidewalls and tread is shaped. By application of heat and pressure, the tire is molded and cured at elevated temperatures.
It is important that the bladder be designed to fit the green tire, so that the bladder remains in contact with the tire. One problem that may occur during expansion of the bladder into the tire mold is that the shoulder portion of the bladder does not engage the shoulder of the tire. This problem may be greater in the case of low aspect ratio tires and run on flat tires. Prior art existing bladder designs were established based on experiences with regular aspect ratio tires. If a bladder for a regular aspect ratio tire is used to shape a low aspect ratio tire, problems may occur due to poor bladder/tire fitment. For example, problems may be due to an undesirable contact sequence or locally too high contact pressure, trapped air, severe rubber squeeze in a local area, and non-uniformity. This can result in uncontrolled distortions in the insert and innerliner geometries during shaping as well as innerliner flow. The bladder shape mismatch may also cause liner buckling in the shoulder area of the tire. Thus an improved bladder shape is desired which more closely matches the green tire geometry and prevents the distortion of the cured tire.